The SET TRANSACTION statement in SQL is used to configure properties for a transaction. Transactions in a relational database management system (RDBMS) ensure the consistency and integrity of the data by allowing a series of SQL statements to be treated as a single unit of work. The SET TRANSACTION statement provides a way to customize the behavior of transactions by specifying various options.
Syntax
Here is the basic syntax of the SET TRANSACTION statement:
SET TRANSACTION [ transaction_properties [, ...] ];
The transaction_properties can include various options that control the behavior of the transaction. Some common options include:
ISOLATION LEVEL
Specifies the isolation level for the transaction. Isolation levels determine the degree to which one transaction is isolated from the effects of other concurrent transactions. Common values include:
READ UNCOMMITTED
READ COMMITTED
REPEATABLE READ
SERIALIZABLE
Example:
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
READ ONLY / READ WRITE
Specifies whether the transaction is read-only or read-write. Read-only transactions are used when no updates are expected, and they may be more efficient in certain situations.
Example:
SET TRANSACTION READ ONLY;
NAME
Assigns a name to the transaction. This can be useful for tracking and managing transactions in certain database systems.
Example:
SET TRANSACTION NAME 'Transaction123';
DEFERRABLE / NOT DEFERRABLE
Specifies whether a transaction is deferrable. A deferrable transaction allows the constraints to be checked at the end of the transaction, while a non-deferrable transaction checks constraints immediately.
Example:
SET TRANSACTION DEFERRABLE;
These are just a few examples of the options that can be set using the SET TRANSACTION statement. The specific options available may vary depending on the database management system being used.
It’s important to note that not all database systems support all options, and the behavior of transactions may differ between database vendors. Therefore, it’s recommended to consult the documentation of the specific database system you are working with to understand the supported options and their implications.